Aerogels are low density solids having low thermal conductivity, a low dielectric constant, and a high surface area, among other properties, due to their fine porous structure. Aerogels consist of a solid network structure, and are made, for example, by extracting a liquid portion of a gel through supercritical fluid extraction while allowing the gel to maintain a solid structure. Polyimide aerogels combine low thermal conductivity and a low dielectric constant with excellent mechanical properties in comparison with silica and polymer-silica hybrid aerogels.
Polyimides are polymers of imide monomers. Polyimides have the general chemical structure shown immediately below.

Polyimide aerogels are excellent insulators due to their high porosity, low thermal conductivity, flexibility, and low density. Accordingly, polyimide aerogels are useful for various applications ranging from lightweight substrates for high performance antennae to flexible insulation for space suits and spacecraft decelerators, such as inflatable structures for spacecraft entry, descent, and landing (EDL) on planets, among other applications. Finding cost efficient precursors to synthesize polyimide aerogels, however, is crucial to large scale manufacturing and commercialization.
Certain polyamines, organic compounds with plural primary amino groups, namely, 1,3,5-triaminophenoxybenzene (TAB), 2,4,6-tris(4-aminophenyl)pyridine (TAPP), octa-(aminophenoxy)silsesquioxane (OAPS), or 1,3,5-tris-(aminophenyl)benzene (TAPB), have been used to cross-link anhydride end-capped polyimide oligomers for synthesizing polyimide aerogels. Polyamine cross-linkers known to be suitable for synthesizing polyimide aerogels have been found to be commercially unavailable at times, and somewhat expensive, thus inhibiting scale-up of manufacturing and production of polyimide aerogels for widespread use.
Moisture resistance is also an important consideration for polyimide aerogels. Hydrophobic silica aerogels have been generally fabricated by modifying the silica surface using hydrophobic groups. Hydrophobicities of cellulose aerogels, resorcinol-formaldehyde aerogel, organic aerogels made with phenolic resole, and methylated melamine have also been formed. Moreover, properties of OAPS cross-linked polyimide aerogels using ODA in combination with either of the rigid diamines p-phenylene diamine (PPDA) or 2, 2′-dimethylbenzidine (DMBZ) have been formed and characterized. For example, DMBZ or PPDA was used to replace up to 100 mol % ODA to optimize the mechanical properties, thermal stability, resistance to moisture, and other properties of the polyimide aerogels. All polyimide aerogels reported previously that include moisture resistant formulation and contain more than 50% DMBZ, however, have contact angles only in the range of 85°-90°.
Thus, an alternative polyimide aerogel and process of manufacture may be beneficial. In particular, a low cost alternative for mechanically strong polymer aerogels may be beneficial.